All political parties risk falling prey to their own mythologies about the voters. In the 1970s, Labour persuaded itself that the public yearned for a more leftwing programme. Yet when Labour offered them one, the voters demurred. For decades, the Liberal Democrats have been similarly convinced that the public would vote for electoral reform. But when given the chance earlier this year, the voters firmly declined.

The Conservative party's equivalent myth is about Europe. Give anti-European feeling its head, runs the belief, and voters will flock to the Tories. At the grassroots of large parts of the party this first myth has now fused with a second, of more recent origin. If only David Cameron had been more anti-European and more traditionally Tory in 2010, it runs, the Tories would have won the general election outright and would not now be cursed with coalition.

It is this combustible fusion that explains both the size of this week's Commons Tory revolt against Cameron over a referendum on EU membership and also why that revolt is so dangerous to the party. For if there is one thing that the great majority of Tories are united about, it is the belief that they can win the 2015 election outright. So strong is this conviction that anything less than the fulfilling of it – even if it takes the shape of a second coalition government with the Lib Dems – would trigger a serious threat to Cameron's leadership.

It is important to understand this point in order to appreciate why Monday's vote is more likely to be the harbinger of things to come than the one-off moment of "making our point" which otherwise loyal MPs would have you believe. The Thatcher generation's aversion to anything European continues to be massively potent within the Conservative party. But the Cameron generation's anger about the failure to win an election that many Tories had persuaded themselves was in the bag cannot be underestimated either.

It is in the nature of such mythologies that they will always trump the facts. But a more objective view would start with the finding in this month's Ipsos Mori/Economist poll that only 1% of voters think Europe is the most important issue facing Britain, and only 4% think Europe is among the most important. The economy, by comparison, rates 50% and 68% on these indexes.

The capacity of true believers to wriggle away from such inconvenient truths is huge. Argue the case and the voters will quickly come round, say some. Remind people of the practical effects, rather than focusing on abstract issues, and it will soon be different, say others. It's all about getting the message past the liberal pro-Europe establishment in the BBC, is a third view. These are the arguments of a political party in denial.

But don't just take my word for that. Much the most devastating rebuttal of such claims this week has come from no less an authority than Lord Ashcroft, the former Tory party treasurer and free-spending mastermind of the party's 2010 key seats campaign. Ashcroft's withering verdict on Monday's revolt is full of ironies, given that his money and expertise was responsible for many of the new intake rebels having the opportunity to vote against Cameron this week in the first place. But he certainly does not mince his words.

"What do we know about voters' priorities?" asks Ashcroft. "We know they are anxious about the economy, in terms of growth and jobs, not just cutting the deficit. We know they care more about the NHS than they think we do, that they believe it is subject to cuts and that they do not know how our reforms are supposed to benefit them … And we know that for many people, the main barrier to voting Conservative is that they do not think we share the concerns of people like them. But which issue has the last week shown still seems to exercise our party above all others?"

Monday's display was damaging, Ashcroft continues, "because it suggested to ordinary voters that the Conservatives are far away from them when it comes to priorities – the most important issues facing the country, and their families". Instead, he says, "we are back in the territory of telling voters why they should share our priorities, instead of showing that we share theirs".

Ashcroft has consistently proved himself to be an unsentimental judge of the party's electoral performances. The Tory party would be well advised to take his verdict seriously this time, too. It is true that Tory arguments over Europe in the 2010s are less ferocious than in the 1990s – so far, at any rate. As the ancients said, one never steps into the same river twice. But the Tories are deluding themselves if they think the issues are less serious. Under Cameron, as under John Major, there is still an argument between pragmatists and fundamentalists. And voters are practical people; they also have longer memories than they are given credit for.

The politics of the next few years will be shaped more than anything else by the need to offer practical answers for dealing with bad times. The voters recognise the need to hunker down as best they can. They will accept their share of sacrifices if they can ride out the storm. The political argument will be about whom you trust most to help you hold on to what matters most – your job, your house and your essential services. It will be about getting through, with as few losses as possible, to better times. Aspiration and vision will matter less, except perhaps in the Scottish context, than they have done in recent years. Those things will mostly be for tomorrow.

The Conservative party risks looking seriously out of touch by focusing on Europe as it did this week. The overriding issue in Europe is practical, equipping the European economy to survive and then grow again. Arguments about treaties and powers are simply secondary. Yet large parts of the party remain addicted to them. Many Tories are more worried about the threat from Ukip in the European elections in 2014 than about stabilising the eurozone now. These are not the priorities of a party that wants to win the argument about how to see Britain through the storm.

Cameron and George Osborne know this. So does Ashcroft. Lots of Tories just look the other way. But knowing it does little to resolve the Tory dilemma. If they lose votes to Ukip on their right, it follows they must win more votes in the centre to capture that elusive overall majority. Cameron failed to pull it off in 2010. And after Monday, he looks more like failing to do it in 2015 as well.